The subject application is a substitute for prior application Ser. No. 07/135,576 which was, in turn, a continuation in part of prior application Ser. No. 06/853,134, both now abandoned.
With the notable exception of the United States, all of the world's industrialized nations have substantial portions of their railway trackage electrified, and these lines carry well over half of the world's railway traffic. In contrast, those portions of the trackage in the United States that are electrified are used almost exclusively for intercity and commuter traffic along narrow corridors.
With only 1800 km (1100 mi) of trackage electrified out of a total trackage of some 300,000 km (190,000 mi), virtually all freight haulage in the United States is conducted with diesel-electric locomotives. This includes coal haulage in unit trains over dedicated branchlines between mines and power stations. That is, railways constructed specifically to move coal from mine to power station rely almost exclusively on oil-fueled locomotives. Of all such branchlines in North America, only a handful use electric power to haul coal for the purpose of electric generation.
Considering that roughly one-third of the available coal-fired power generating capacity of the typical power district is unused for about two-thirds of the time and that roughly one-quarter of the available power is unused for about three-quarters of the time; this reliance on oil-fueled locomotives is all the more surprising in terms of this excess generating capacity until one considers the cost of overhead catenary electrification.
Electrification costs are so substantial that even when all of the advantages of catenary-electric traction over diesel-electric traction are taken into consideration for coal haulage, such as well over twice the locomotive service life with less than half the maintenance costs so that two catenary-electric locomotives can readily do the work of three diesel-electric locomotives, it is still not economically feasible to electrify existing coal-hauling lines by conventional means. This is the case despite the fact that for branchlines less than 100 km (62 mi) in length all of the electrical gear can be located at the power station with neither the need for substations nor the need to purchase, store or distribute diesel fuel.
Virtually all recent branchline electrification is confined to new railway construction involving the development of new coal fields and the construction of new power stations in which the cost of catenary electrification is a small portion of the overall cost of the project. For existing coal-haulage branchlines however, it is the substantial cost of conventional catenary construction that constitutes the only obstacle to electrification, despite the availability of excess power generating capacity. Nevertheless, the conventional catenary system is the only construction presently considered for branchline electrification.
The source of the high construction costs of conventional catenary construction is discussed herein, as are several schemes that have been proposed to ameliorate the disadvantages of conventional construction but which in fact introduces difficulties of their own, and these are compared with an alternate construction which utilizes the electronically-tracking pantograph.